The objective of the current study is to evaluate the differnce between mibefradil and losartan in the change of mean trough sitting diastolic blood pressure (SDBP) measurements after 8 weeks of active treatment. This study includes a 4-week placebo run-in period followed by an 8-week treatment period. During the first 4 weeks of the treatment period, the patients receive either mibefadil (50mg), or losartan(50mg). At week 4, patients responding to the study drug, mean trough SDBP<90mmHg, will continue on the same study drug at the same dose for four more weeks. Patients with mean trough SDBP>90mm Hg, will titrate up to a final dose of 100 mg once daily for the remaining 4 weeks through weeek 8.